1. Field of the Invention
The present invention relates to a tool holding mechanism for use in an assembly apparatus for semiconductor devices, such as an inner lead bonder, outer lead bonder, bump transfer bonder, pellet bonder, etc.
2. Prior Art
Tool holding mechanisms for use in bonders includes a tool holder to which a tool is fastened and an attachment section mounted to a tool-holding part of the bonder so that the tool holder is attached to the attachment section.
In bonders, it is desirable that the entire undersurface of the tool uniformly contact the bonding surface of the sample.
Mechanisms equipped with an automatic fit-adjusting means, such as those described in, for example, Japanese Patent Application Laid-Open (Kokai) No. 63-169730 and Japanese Patent Application Laid-Open (Kokai) No. 63-169731, are known as conventional tool holding mechanisms for use in bonders. In these mechanisms, the tool holder and attachment section are connected via a spring. Accordingly, when the tool is pressed against a sample, the undersurface of the tool fits against the bonding surface of the sample with the spring bent.
The mechanism in the prior art insures the flatness of the tool in the XY plane, and no consideration is given to adjustment in the direction of rotation about an axial center of the tool (i.e., the .theta.-direction).
Conventionally, adjustment in the .theta.-direction is accomplished in a following manner: As shown in FIG. 12, the tool is lowered so that a pressure mark of the tool is made on bumps 2 of a chip 1, and the discrepancy in the .theta.-direction is examined. Then, the fastening screw of the tool is loosened to perform the adjustment by turning the tool directly by hand.
Thus, in the prior art, adjustment of the tool in the .theta.-direction is accomplished by turning the tool directly by hand. Accordingly, application of the tool pressure marks and adjustment of the tool must be repeated several times, requiring considerable time and a high degree of skill.
Adjustment of the tool in the X and Y directions is accomplished by automatic fit adjustment. Accordingly, such adjustment requires no particular adjustment work. However, since the tool is pressed against the leads of the sample (which possesses elasticity) via a spring, slipping may occur at the time of the pressing. Because of such slipping, the tool is pressed against off-center portions of the leads instead of against the center of each lead. Consequently, the bonding precision and bondability are poor, causing faulty bonding.